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64               PRACTICAL  ORGANIC  CHEMISTRY

over small pieces of calcium chloride. It is decanted or
filtered from the calcium chloride and distilled. The distillate is
collected at 130  132. The yield is nearly equal to the
weight of bromine taken.

Properties.  Colourless liquid, which solidifies, at o to a
crystalline mass and melts at 9 ; b.p. 131'S0 ; sp.gr. 2*19 at if.

Reaction. Attach a 100 c.c. flask to a short upright con-
denser (see Fig. 86) and to the upper end of the condenser
attach a vertical delivery tube, dipping into an ammoniacal
cuprous chloride1 solution. Pour i  3 c.c. of ethylene bromide
into the flask with 4 times its volume of strong methyl alcoholic
potash, which is prepared by boiling methyl alcohol with excess
of caustic potash on the water-bath with upright condenser. On
gently heating, a rapid evolution of acetylene occurs and the
characteristic brown copper compound (C2H2Cua,H2O) is pre-
cipitated from the cuprous chloride solution.

Acetyene.

See Appendix, p. 237.

PREPARATION 5.

Acetaldehyde, CH3.CO.H

Liebig, Annalen^ 1835, 14, 133 ; Staedeler, /. prakt. Cheni.,
1859, (076, 54-

100 grms. potassium bichromate
420 c.c. water.

A mixture  of 100 grms.   (125   c.c.)   absolute   alcohol
and 140 grms. (75 c.c.) cone, sulphuric acid.

100  c.c.  methylated   ether,   which   has   been   left   to
stand  over solid  caustic potash  for a few  hours,  and
then distilled off from the water-bath.
A round flask (i-| litre) is provided with a double-bored cork.

washed once or twice by decantation and dissolved in a strong solution of ammonium
chloride. When required a little ammonia is added sufficient to give a clear blue
solution.